Method and apparatus for producing high temperatures by a magnetic field surrounding an electric arc



April 8, 1969 w. w. SALISBURY 3,437,862 METHOD AND APPARATUS FORPRODUCING HIGH TEMPERATURES BY D SURROUNDING AN ELECTRIC ARC 1 Y AMAGNETIC FIEL Filed July 19, 1957 Sheet a M wp m JM w m 3,4375862 RES BYC 2 April 8, 1969 w. 'w. SALISBURY METHOD AND APPARATUS FOR PRODUCINGHIGH TEMPERATU A MAGNETIC. FIELD SURROUNDING AN ELECTRIC AR Filed July19, 1957 Sheet April 8', 1969 w, w, L SB Y 3,437,862

METHOD ND APPARATUS FOR raonucxue HIGH TEMPERATURES BY I A MAGNETICFIELD suaaounnme AN ELECTRIC ARC Filed Jul 19,1957 I Sheet 3 or 13 no nnon jy/ a Winfield zji lfi'a f'satg I CA fiorzzqq April 1959 I N w. w.SALISBURY 3,437, METH OD AND-APPARATUS FOR PRODUCING HIGH TEMPERATURESBY v A MAGNETIC FIELD SURROUNDING AN ELECTRIC ARC Filed July 19,1195?Sheet 4 of 13 I ,l I J07 A ril 8, 1969 w. w. SALISBURY 3, 3 2

. I METHOD AND APPARATUS FOR PRODUCING HIGH TEMPERATURES BY v I 1 AMAGNETIC FIELD SURROUNDING AN ELECTRIC ARC Filed July 19. 1957 Sheet 5of 13 122 We n for Mm zezdldazwm 5y iiorzzeg April 8, 1969 w. w.SALISBURY 3,437,862

METHOD AND APPARATUS FOR PRODUCING HIGH TEMPERATURES BY RROUNDING ANELECTRIC ARC A MAGNETIC FIELD SU Filed July 19. 1957 Q of 13 Sheet I 5 wr I I I 5 1 April 8, 1969 w. w. SALISBURY 9 3 23. w URROUNDING ANELECTRIC ARC Sheet 7 of 13 METHOD AND APPARATUS FOR PRODUCING HIGHTEMPERATU A MAGNETIC FIELD 5 Filed July 19, 1957 April 8, 1969 w. w.SALISBURY .;5 ;13;7,862

B D SURROUNDING AN ELECTRIC ABC 8 METHOD AND APPARATUS FOR PRODUCINGHIGH TEMPERATU A MAGNETIC FIEL Filed July 19, 1957 Sheet Zioz-zzeg P" 3,11969 w. w. SALISBURY 3,437,352

METHOD AND APPARATUS FOR PRODUCING HIGH TEMPERATURES BY A MAGNETIC FIELDSURROUNDING AN ELECTRIC ARC Filed July 19, 19s? Sheet 9 of 1s A rll 8,1969 w. w. SALISBURY 3,437,862

METHOD AND APPARATUS FOR PRODUCING HIGH TEMPERATURES BY A MAGNETIC FIELDSURROUNDING AN ELECTRIC ARC Filed July 19, 1957 Sheet /0 of 13 W. W.SALISBURY METHOD AND APPARAT Aprll 8, 1969 3,437,862

US FOR PRODUCING HIGH TEMPERATURES BY A MAGNETIC FIELD SURROUNDING ANELECTRIC ARC Filed July 19, 1957 Sheet of 15 April 8, 1969 W. SALISBURYMETHOD AND APPARATUS FOR PRODUCING HIGH TEMPERATU A MAGNETIC F FiledJuly 19, 1957 3,437,862 RES BY IELD SURROUNDING AN ELECTRIC ARC Sheet 3of 15 Trigger 85' 301 67 57 57 J/ F l" T T" 1: 2 T rz'gger 1 415 61 135l- Powr fi za Z 26' Power T Winfield Zd 5a Zz'sazy April .8, 1969 w. w.SALISBURY 3,437,852

METHOD AND APPARATUS FOR PRODUCING HIGH TEMPERATURES BY 19A57MAGNETICFIELD SURROUNDING AN ELECTRIC ARC Filed July 19,

Sheet 13 of 1s Nmm United States Patent Olfice 3,437,862 METHOD ANDAPPARATUS FOR PRODUCING HIGH TEMPERATURES BY A MAGNETIC FIELDSURROUNDING AN ELECTRIC ARC Winfield W. Salisbury, Palo Alto, Calif.,assignor to Zenith Radio Corporation, a corporation of DelawareContinuation-impart of application Ser. No. 510,311, May 23, 1955. Thisapplication July 19, 1957, Ser. No. 673,077

Int. Cl. H013 61/28; H05b 31/26; G21b 1/00 US. Cl. 313-161 36 ClaimsThis application is a continuation-in-part of the copending applicationof Winfield W. Salisbury, Ser. No. 510,311, filed May 23, 1955, forMeans To Produce High Temperatures in Gases, and assigned to the sameassignee as the present application.

This invention relates to the heating of materials in the gaseous statewhile substantially preventing material loss of energy from the heatedbody by convection from the heated zone or conduction to the walls ofthe container. Since the relative proportion of the energy introducedinto a body of gas which is lost through these two causes increases veryrapidly with temperature, the invention finds its greatest value in theproduction of ultra-high temperatures, and particularly of tempertaureswhich are above the melting point or even above the vaporization pointof refractory materials which are available for containing the heatedmaterial, but the principles involved are of general utility, and can beapplied in heating to any temperature under conditions such that the gasto be treated becomes ionized. There is thus no definite lower limit tothe applicability of the invention. The upper limit is set by a numberof factors which will vary with the material being treated; this may bethe point at which the loss of energy by radiation occurs as rapidly asenergy can be supplied, or it may be the point at which the pressuregenerated by the heated gas becomes uncontrollable. As will be shownhereinafter, the expedients employed in the invention make even theselimitations less restrictive than would appear at first sight, and,since all known substances become gaseous at sufiiciently hightemperatures, the restriction to gases is merely a restriction as tostate and not as to material.

There are various purposes for which the production of very hightemperatures is valuable. Many reactants will take place under hightemperature which will not go under other conditions. There is a generalrule of thumb as regards chemical reactions, for example, to the effectthat the speed of reaction approximately doubles for each rise intemperature of degrees centigrade. High temperature spectroscopy can bean extremely valuable tool, both in basic research and in the control ofindustrial processes, and there are various other purposes for which theability to produce ultra-high temperatures would be of value. In itsbroadest aspect, the present invention is considered to reside in theproduction and control of extremely high temperatures for all purposesand is not limited to the application of the temperatures so produced tospecific uses.

The invention is also directed to methods and apparatus for inductingcontrolled thermo-nuclear fusion, in which the energy liberated isavailable as a power source, or a source of radiation of manageableproportions, instead of as a catastrophic explosion.

It is generally recognized that thermo-nuclear reactions requiretemperatures in the general neighborhood of several million degreesabsolute. So far as results have been published up to the present time,the only effective means of raising materials to such temperaturesartificially have been through the use of atomic fission reactions,conditions leading to an explosive or catastrophic release of 3,437,862.Patented Apr. 8, 1969 energy. Means of controlling the release of energyin such combined fission-fusion reactions are not at present known.

At temperatures within the reactive range all materials are in thegaseous phase, molecules are dissociated into their constituent atomsand the atoms are ionized. In order that the collisions between nucleibe sufficiently probable so that the reaction will be self-sustaining,the gas is usually maintained at an elevated pressure, preferablycorresponding to many atmospheres, even at the start of the reaction andas the reaction progresses in a given volume, of gas, even though somedegree of expansion be permitted, the pressures developed are enormous,exceeding the crushing strength of most available materials if theypersist for an appreciable time.

If the nuclear fusion action is to take place in a small volume of gas,there arises the difiiculty of pouring energy into the gas faster thanit is dissipated from it. Loss of thermal energy from a given volume ofmaterial occurs by convection, by conduction, and by radiation, thefirst two of which are directly proportional to the area of the surfaceenclosing the volume. (The plasma may not be considered as a black body,so the radiation loss is a volume phenomenon.) Since for a sphere, whichhas a minimal surface for a given volume, the ratio of surface area tovolume varies inversely with the diameter, it is more difi'icult, withrespect to heat loss, to raise a small volume of material to a giventemperature than a large one.

Thermo-nuclear reactions which will liberate energy are probably mostpractical for materials of low atomic number. Both atomic species of lowatomic number and those of high atomic number may liberate energy iftransformed into species lying in the middle range, that is, energy maybe released at low atomic numbers through fusion and at high atomicnumbers through fission. It is conceivable that fission as well asfusion may occur at sufficiently elevated tempertaures. The chiefreactant in reactions which should occur most readily are hydrogen, andits known isotopes, deuterium and tritium. Throughout this specificationthe word hydrogen, except when qualified by the term isotope, will beused to designate H that isotope wherein the nucleus comprises a singleproton, H and H being designated as deuterium and tritium respectively.Another feasible source is He helium of atomic weight 3.

Hydrogen isotopes, as such, can be made to react with lithium (atomicnumber, Z=3), berryllium (2:4), and possibly boron (2:5), as well aswith each other and with He Reactions between deuterium nuclei,resulting in approximately equal amounts of tritium and He plus neutronsand energy, are particularly attractive, but deuterium-lithium,tritium-tritium or deuterium-tritium reactions are typical of otherfeasible reactions.

With a hydrogen isotope as one of the major reactants, the radiationloss becomes a small proportion of the power to be supplied to initiatethe reaction. Hydrogen is a very poor radiator of energy of thewavelengths developed by it at the temperatures here considered, and itsisotopes are only slightly better radiators. The major loss of energy ina body of hot ionized gas occurs through conduction to the walls of thecontainer which may enclose it, and since conduction is, to at least afirst approximation, a linear function of temperature difference, lossof energy by conduction from even a small volume of gas tends to be veryfast indeed.

Something of the magnitude of the problems involved can be appreciatedfrom a numerical example. A onemillimeter sphere of deuterium atatmospheres pressure and 1000 degrees Kelvin has a theoretical energycontent equal to the amount of chemical energy of about 0.0086 pound or.011 pint of gasoline. Raised to a temperature of 10 million degreesKelvin, the pressure, if

maintained within this same volume, would increase to about 4 or fourmillion atmospheres, or somewhere in the neighborhood of seventy-sixmillion pounds per square inch. If the problems of heat less byradiation, conduction, and convection could be solved, so that all ofthe energy supplied to a volume of deuterium were retained by it, thetotal energy required to dissociate, ionize, and heat it to the reactingtemperature would be only about of the energy released, and once enoughenergy were supplied to initiate the reaction the remainder of theenergy would come from the reaction itself. The problems that arise aretherefore not those of providing enough energy to cause a reaction tostart but those of retaining the energy so that it will not be lostfaster than it is supplied and of containing the reaction products,including the heat generated, so that they can be used in maintainingand elevating the temperature.

The primary object of the invention is to provide means for raisingmaterials in the gaseous state to ultra-high temperatures underaccurately controllable conditions. Other objects are to provide meansfor producing ultrahigh temperatures in a body of gas while preventingexcessive temperature rises in the apparatus wherein such hightemperatures are produced, maintaining such apparatus within a range oftemperature where structural materials retain their strength and normalphysical prop erties; to provide means for heating a small body of gaswithin a larger body without material loss of energy by convection intothe larger body during the heating proc ess; to provide apparatus inwhich a body of gas can be heated within a container without loss byconduction to the walls of the container while the heating is inprocess, so that such loss does not set a limit to the temperature whichcan be obtained in the heated gas; to provide a means for producingultra-high instantaneous temperatures within a body of gas whilemaintaining the average temperature at moderate values; to provide meanswhereby certain materials can be made to absorb very large quantities ofenergy with extremely small loss by convection, conduction, orradiation; to provide heating a paratus wherein the mechanic-a1 stressesproduced by the heating can be sustained for the brief interval requiredby the inertia of the parts of the apparatus rather than throughexcessive weights or cross-sections of the parts; to provide electricalheating apparatus wherein electrical stresses can be maintained withoutthe use of heavy insulators or the danger of break-down of theinsulation which is employed; and to provide apparatus wherein, throughthe use of pulse techniques, the nonlinear relation of the energy lossesto temperature from materials at high temperature can be used to theadvantage of the process rather than to its detriment.

A further and obviously tremendously important object of the presentinvention is to provide a method of and apparatus for initiating acontrollable nuclear reaction of the fusion type. This involves, assubsidiary objects, containing the pressures developed by the reaction;controlling energy losses from a body of gas entering into the reactionto a degree which will permit the necessary temperatures to be attained;providing apparatus in which, within a given reaction chamber, thequantity of material entering into the reaction, and therefore therelease of energy by it, can be controlled; providing a process wherebythe walls of the reaction chamber are not subjected to extreme reactiontemperatures or pressures; and providing an energy source which may beused with either especially purified isotopes of the reactive materialsor preferably, with common isotopes of commercially available materials.

Apparatus for producing high temperatures, constructed in accordancewith the broader aspects of the invention, comprises means fordeveloping a concentrated magnetic field substantially encompassing areaction space, and means for producing a cloud or plasma of ions in thereaction space in the presence of th? magnetic field.

The invention is based on three well-known facts:

First, gases become ionized on heating, and can be completely ionized ateven moderately high temperatures, the heated gas resolving itself intoa cloud or plasma of electrons and positively charged ions;

Second, the temperature of a heated gas is defined by the averagekinetic energy of its component particles;

Third, a charged particle entering a magnetic field transversely will bedeflected by that field from its straight line course into a circularpath, while such a particle traveling longitudinally of the field willbe undeflected.

In accordance with the invention, means are provided for establishing alocalized and very intense magnetic field which substantially surroundsor encompasses a reaction space containing a small volume of gas to beheated, this volume being most conveniently a small portion of a largersurrounding body of gas. The small volume mentioned is heated andionized, preferably by passing an electric discharge such as a sparkthrough the reaction space in a direction along a plane or axis ofsymmetry of the field which encloses it. To the extent permitted by theenclosing field, the thermal velocities imparted to the gas ions arerandom, tending to cause them to escape from the heated zone, but sincethe particles are all charged they are immediately deflected by thesurrounding field and forced back into the path of the spark, and arethereby prevented from escaping into the surrounding body of gas to heatit by convection or from hitting the walls of the container or otheradjacent structure to impart their energy to the latter as heat lost byconduction. The temperature to which the gas within this small volumecan be raised is herefore limited only by the strength of the magneticfield, which determines the maximum energy of the particles which can beso deflected as to return toward the heated zone before escaping orstriking the surrounding structure, and by the kinetic energy which canbe applied to the ions in the heated zone by the spark.

In an exemplary form of the apparatus, the magnetic field whichsurrounds the volume of gas to be heated is developed by passing currentthrough an inductance coil structure comprising a pair of similar,coaxially arranged coils which have a small internal diameter ascompared with the width of the conductor in each coil as a whole. Thetwo coils are spaced along the common axis by 'a distance which is ofthe same order of magnitude as and is preferably approximately equal totheir internal diameter, the space defined by the internal diameter ofthe coils and the dimension of the interspace between them comprisingthe aforementioned reaction space containing the body of gas to beheated. The coils are connected so that they will carry substantiallyand preferably exactly the same current at the same time; i.e., they maybe connected either in series or in parallel but the former is preferredas requiring less careful balancing to make the coils electricallyidentical. Each of the two coils may comprise a single edgewise turn ofstrip material whose leads are brought out face-to-face to minimize thelead inductance. Current may circulate through the coils either in thesame or in opposite directions, each of these arrangements havingcertain advantages.

If the circulation is opposite, so that the fields produced thereby areoppositely directed along the common axis of the coils, a space isproduced midway between the coils which is substantially field-free, thelines of force from both fields combining to pass out radially :betweenthe coils as a field of radially decreasing strength. Means are providedfor passing through these coils pulses of current which may be of aduration of time less than a microsecond up to and including pulses ofmicroseconds and even longer each, depending upon the configuration ofthe apparatus used. With a single coil of this character, extremelypowerful magnetic fields can be established at the center of the coil.With the two coils bucking, the inductance of the system is stillfurther reduced so that even stronger fields can be developed. Even witha single coil, field strengths up to ten million gauss have beenestablished and maintained for periods of the order mentioned.

A pair of electrodes is mounted axially of the two coils, forming aspark gap which spans the interspace between them, and means areprovided for establishing a pulse of energy of suflicient voltage tojump this gap during the passage of the current pulse through the twocoils.

If the purpose of the arrangement is to examine the spectrum of air atultra-high temperatures no further apparatus is required. In general, itwill be other materials whose examination or treatment is necessary ordesirable. In this case the arrangement described will be enclosedwithin a gas-tight container, preferably provided with exhaust ports forfirst removing the air and pressure ports for introducing the gas orgases whose temperature is to be raised. In this event a window may alsobe pro vided, through which the volume of incandescent gas can beobserved.

To induce controlled thermo-nuclear fusion, the reaction space ispermeated with one or more of the aforementioned nuclear reactants andthe magnetic field must be of megagauss intensity, i.e., in excess ofone million gauss, and preferably of the highest intensity obtainable.Moreover, the energy supplied to each particle of the reactant withinthe reaction space encompassed :by the magnetic field must be at leastseveral orders of magnitude greater than the quantum threshold forionization of the particles. As before, the magnetic field may beco-directional or it may comprise two co-linear, oppositely directedfields of the intensities described, closely apposed, in which casethere will be formed on the common axis between them a small volumewhich is relatively fieldfree owing to the mutual repulsion of the linesof force constituting them. The energy required to initiate the reactionmay be supplied by an electric spark passed through the gas contained inthe reaction space and enclosed by the field, in the direction along theaxis of the magnetic field. Where co-directional fields are employed, itis only with great difiiculty that a spark can pass or that chargedparticles, either electrons or nuclei, can traverse the space in anydirection other than the axial direction of the field; if oppositelydirected fields are employed, the spark may be readily passed either inthe axial direction or in a transverse direction midway between the twocoils. The passage of the spark dissociates, ionizes, and heats the gas,so that the particles comprising the gas acquire high energies whichtend to cause them to escape from the area of the discharge. Owing tothe fact that they are necessarily all ionized, the particles cannotpenetrate the field but are deflected back into the region wherein thespark is passing, in their motion themselves setting up magnetic fieldswhich tend to render the space through which the spark is actuallypassing field-free, while concurrently increasing the magnetic fielddensity in the surrounding region. The encompassing magnetic fieldtherefore acts as a highly elastic membrane, expansible to a limiteddegree but becoming increasingly rigid as it expands.

Un-ionized atoms of the surrounding gaseous atmosphere can enter freelythrough this magnetic wall or membrane, since, being uncharged, they arenot deflected by the magnetic field. Once having entered the reactionspace, however, they are immediately ionized and cannot escape and hencethe membrane acts like one of the semipermeable type.

It should be readily apparent that as long as the field persists,practically no energy can be lost by either conduction or convection. Assoon as the field is permitted to collapse, however, the highlyenergetic ions immediately escape into the much larger surroundingvolume of gas, which is thereby raised to a temperature which is ameasure of the average thermal energy of the entire volume of gasincluding that in the reaction space. This is the weighted average ofthe absolute temperatures of the two volumes, and by choosing a suitablevolume for the container or reaction chamber the temperature of thentire gas volume can readily be controlled and held within feasiblelimits. It is this temperature, and not the temperature of the actualreaction space that determines the temperature rise in the reactionchamber as a whole.

Those portions of the reaction chamber which are necessarily close tothe reaction volume will, of course, have their surfaces raised to amuch higher temperature. The rate of thermal conduction in the metalswhich would normally 'be used is, however, relatively slow, so that thepenetration of the heat Waves in the intervals between reactions is notgreat, the gas is expanding and cooling as it is released, and much ofthe energy absonbed by the surfaces close to the reaction volume isreturned to the gas. More is conducted away and the parts of theequipment closest to the reaction can be water-cooled if necessary.

The final problem is that of withstanding the forces involved. As hasbeen pointed out, no materials now known could directly support theseforces. The forces resulting from the pressure within the reactionvolume are transferred to the coils which carry the currents generatingthe magnetic field through the medium of the field itself. Whatwithstands these forces is the inertia of the coils and of the otherparts of the structure wherein the reaction takes place. The parts cando this because of the very short intervals during which the field ismaintained, and although the forces acting are very large their impulse,in a period of the order of microseconds, is not excessive. Thereforethe reaction can be contained within chambers of readily realizablephysical size and strength.

From the above, it will, of course, be recognized that the invention isdependent upon the effective use of pulse techniques. By liberatinglarge amounts of energy during very short intervals and so spacing thoseintervals that the recurrence time is long in comparison with theportion thereof during which energy is released, the average can be madeof manageable proportions and the problems of strength, heat loss, andrelated matters can be solved by fairly conventional techniques.Indicative of the usefulness of the device as a power source, it shouldbe quite evident that the reaction chamber can :be made one unit of aclosed circulatory system for the hydrogen isotope used as one of thereactants. With this arrange ment the over-all system can become a hotgas gener rator, the energy of the reaction transferred through a heatexchanger and used in any manner desired, and the cooled gas returned tothe system for further reaction. The very high specific heat of hydrogenand its isotopes is favorable to such use.

Furthermore the method and apparatus are useful as providing anextremely prolific neutron source if the proper nuclear reactants areused. Such neutron generation (and power generation as well) is possibleusing the generally available forms of the reactive substances. Forexample, hydrogen isotopes will react with lithium or with each other toproduce a plentiful supply of neutrons plus power. The lithium can beintroduced into the reaction area by coating one or both of theelectrodes, through which the spark is introduced into the system, withlithium or one of its salts, preferably lithium deuteride, or thesparking electrode can be provided with a lithium core. The heat of thespark evaporates the coating material into the reaction space, and ifthe salt is used it is dissociated into deuterons and lithium nucleiboth of which are capable of entering into the fusion reaction.

The features of the present invention which are believed to be novel areset forth with particularity in the appended claims. The organizationand manner of operation of the invention, together with further objectsand advantages thereof, may best be understood by reference to thefollowing description taken in connection with the accompanyingdrawings, in the several figures of which like rcference numeralsidentify like elements, and in which:

FIGURE 1 is a diametric cross-section of an illustrative embodiment ofthe device, the connections to an exhaust and to a pressure system beingshown schematically;

FIGURE 2 is a cross-sectional view of the device of FIGURE 1, the planeof section being indicated by the dashed line 2-2 in the first figure;

FIGURE 3 is an exploded perspective view of the coil assembly of thedevice of FIGURES 1 and 2;

FIGURE 4 is a diagram, partly schematic and partly in block, of theelectrical connections of the device;

FIGURE 5 is a fragmentary view, on an enlarged scale, showing thegeneral direction of the magnetic field in the vicinity of the spark-gapwith the magnetizing coils connected to produce opposing fields;

FIGURE 6 is a view generally similar to that of FIG- URE 5 illustratingthe general direction of the lines of magnetic force with the magneticfields in the same direction;

FIGURE 7 is a view similar to those of FIGURES 5 and 6 of a modifiedconstruction for providing the desired field configuration with a singlecoil;

FIGURE 8 is a vertical cross-sectional view of a modified form of thedevice; 7

FIGURE 9 is a cross-sectional view, in plan, of the device illustratedin FIGURE 8;

FIGURE 10 is a developed view of the coils employed in the apparatus ofFIGURES 8 and 9, as used for parallel excitation with the fields aiding;

FIGURE 11 is a generally similar developed view of the coil constructionfor use in the apparatus of FIG- URES 8 and 9 with the coils connectedin series and the fields bucking;

FIGURE 12 is an exploded perspective view of the inductance coilstructure used in another embodiment of the invention;

FIGURE 13 is a cross-sectional view, similar to that of FIGURE 1, of anembodiment of the invention incorporating the inductance coil structureof FIGURE 12;

FIGURE 14 is a cross-sectional view, taken along the line 1414 of FIGURE13;

FIGURE 15 is a cross-sectional view taken along the line 15-15 of FIGURE14;

FIGURE 16 is a cross-sectional view, similar to those of FIGURES 1 and13, of an additional embodiment of the invention;

FIGURE 17 is a cross-sectional view taken along the line 1717 of FIGURE16;

FIGURES 18a and 18b together constitute an exploded view of theinductance coil structure employed in the embodiment of FIGURES 16 and17;

FIGURE 19 is a cross-sectional view, similar to those of FIGURES 1, 13and 16 of still another embodiment of the invention;

FIGURE 20 is a cross-sectional view, taken along line 20-20 of FIGURE19;

FIGURE 21 is an exploded perspective view of a portion of the inductancecoil structure of the embodiment of FIGURES 19 and 20;

FIGURE 22 is an end view of the structure shown in FIGURE 21;

FIGURE 23 is a cross-sectional view, taken along the line 23-23 ofFIGURE 22;

FIGURE 24 is a cross-sectional view, similar to those of FIGURES 1, 13,16 and 19, of a further embodiment of the invention;

FIGURE 25 is a cross-sectional view of still another embodiment of theinvention;

FIGURE 26 is a schematic circuit diagram of a power supply system whichmay be employed with any of the illustrated embodiments in accordancewith another aspect of the invention;

FIGURE 27 is a cross-sectional view of a further embodiment of theinvention;

FIGURE 28 is a cross-sectional view, taken along the line- 28-28 ofFIGURE 27; and

FIGURE 29 is a cross-sectional view, taken along the line 29'29 ofFIGURE 27.

In the form of the invention illustrated in FIGURES 1 and 2, thecontainer which houses the active elements of the apparatus comprisesprimarily a pair of heavy metal discs 1 and 3 which are preferablyformed of a material which is resistant to attack by either the gas tobe heated or by any reaction products which may be formed in theoperation of the device. For many purposes stainless steel is suitable,and it is of some advantage to use one of the grades of this materialwhich is substantially non-magnetic. As will be understood from thegeneral description of the apparatus above given, there will beextremely intense magnetic fields in the immediate neighborhood of thecontainer and it is, of course, desirable to minimize the losses due tothe electrical or magnetic induction in the container. Because of thebrief duration of the pulses employed in operating the device, bothelectric and magnetic effects come into play and losses may be reducedby making the surface of the material either highly resistant or highlyconductive. For the later purpose plating the inner surface of the discswith gold, silver or copper is effective where these materials have thenecessary chemically non-reacting characteristics. Where such a platingis restored to, its effect is to reduce somewhat the effectiveinductance of the coils, which is desirable; in any event the losses areof relatively small moment in comparison with the total amount of powerutilized in the operation of the apparatus.

A circle of holes is formed near the periphery of both of the discs forreceiving stud bolts 5, which clamp the container together. Disc 1 isprovided with a port 7 for attachment to a pressure system including aduct 9 having a control valve 11 therein for admitting the gas to betreated. The duct can connect to a gas cylinder 13 or other source ofgas under pressure, and the system is shown as being provided with apressure gauge 15.

The disc 1 is also shown as being provided with a window for observingthe area wherein the heating is taking place. This window is shown ascomprising a bore 17 which aims diagonally through the disc at thesparking area and is counter-bored and threaded to receive a gasketwasher 19, of copper or other soft metal, upon which rests a heavy discof quartz or glass 21 held tightly in place against the gasket by ahollow screw 23. For many purposes a synthetic plastic such as thefluorine-substitution plastic, polytetrafluoroethylene, manufactured andsold under the trademark Teflon forms a suitable gasket material. Afixed spark electrode 25 projects inwardly of the container from thecenter of disc 1.

The disc 3 is formed with a central aperture which is counter-bored andthreaded to receive a spark plug 27, whose central conductor 29 facesthe electrode 25 to form the spark gap through which is delivered theenergy which heats the gas to be treated. The spark plug can be ofsubstantially the type used in automative practice, the conductor 29being surrounded by an insulating sleeve 31 of ceramic, mica or othersuitable insulation. Gaskets or shims 33 provide a seal against the gaspressures developed with in the container. It may be noted that when thedevice is operated at the higher internal gas pressures that will bereferred to later, requiring high voltages in order to strike the spark,additional insulation must be provided externally of the apparatus forthe lead to the spark point or electrode 29. Because this is notdirectly pertinent to the invention, such additional insulation is notshown in the figure. An exhaust port 35 connects with a suitable vacuumline 37, closed ofi by a valve 39 and provided with a vacuum gauge 41,which leads to a vacuum pump 43.

The circumferential Walls of the container are built up from conductiverings 47, formed integrally with the magnetic coils themselves,alternating with rings 45, of

insulating material, separating the coils. In the modification of themethod first to be described the coils are arranged to establish coaxialbut oppositely directed mag netic fields, the exciting currentstherefore circulating through the two coils in opposite directions. Eachcoil is formed from two flat plates, preferably of copper, although theymay be of steel (for rigidity) copper plated to carry the current.Because of the short duration of the pulses used the major portion ofthe current is carried by the surface layers of the coils in any event,owing to skin effect. Tungsten, with or without copper plating is also asuitable material for the coils; it has great mechanical strength, fairconductivity, and its high density gives it high inertia to withstandthe impulse of the large forces that are developed during the currentpulses. For the hightemperature purposes for which this reaction chamberis intended, insulation rings 45 may be constructed of dense, refractoryceramic, sealed to the adjacent metal by a high-temperature cement.

The construction of the coils and the conductive rings 47 is best shownin FIGURES 2 and 3. Each coil is formed in two halves, of very nearlythe same shape, which are brazed, soldered, or welded together to form asingle turn. Each of the component parts of the coil comprises a ring 47of the same outside diameter as the discs 1 and 3, this ring beingperforated around its circumference to pass the clamp bolts 5 and aninsulating sleeve 49 which surrounds each bolt. Projecting outwardlyfrom one side of the ring is a tab 51 which is electrically andpreferably physically continuous with a strip supply lead 53.Designating the entire upper coil (as viewed in FIGURE 2) by thereference character 55, the inwardly projecting tongue 55 of the halfwhich is fully visible in the figure extends from the full line 55' in acounterclockwise direction, around one half of the minute circularaperture 57 which forms the internal diameter of the coil, to the line59 where it is brazed or soldered to the other half of the coil. Theother half of the coil 55 has a tongue of nearly the same shape, butturned over side for side, the projecting tab which forms the half 55 ofthe coil ex tending beneath the half 55 from the dotted line 55' in aclockwise direction around to its junction with tab 55 at the line 59.The two halves differ in that the half 55 is bent downwardly at thegeneral position of the line 55 into the plane of the other half of thecoil.

The second coil 61 is formed in exactly the same fashion, but is turnedover, with the inner or unbent conductors being joined externally of thecontainer at their projecting tabs 51 by a short connecting link 63.Supply leads 53 connect to the outer conductors of the coils, overlyingeach other closely, with a layer 65 of insulation between them.Externally of the reaction chamber the insulation 65, which separatesthe leads, need not be refractory. It should, however, be low-loss andshould have considerable mechanical strength.

Coils of this character are characterized by very large current-carryingcapacity and very low inductance. The currents carried by adjacent coilsare in opposite directions and therefore, insofar as the magnetic fieldsof the coils overlap, they are bucking, so that their mutual inductanc'esubtracts from the self-inductance of the individual leads. In spite ofthe very considerable capacity between the leads, the rise-time ofpulses in the coils can be made very short.

Extremely high magnetic fluxes can be developed in the small centralapertures 57, fluxes up to gauss and more having been measured for shortperiods of the order of magnitude of those involved in the process heredescribed. With fiuxes of this order of magnitude developed in theneighborhood of the coils and their leads,-it will be seen that veryhigh repulsive forces exist which would tend to disrupt the apparatus ifthey continued for any protracted length of time. What prevents suchdisruption, as has already been indicated, is the inertia of thestructures, which tend to acquire only low velocities because of thesmall impulse of the acting forces and the cushioning of these forcesduring the periods in which they are acting by the elasticity of thematerials. Experience has shown that only moderate restraining forcesare required to hold the leads together externally of the reactionchamber and that even in the experimental apparatus illustrated theinertia of the coils is sufficient to withstand the forces operativeinternally of the reaction chamber.

The construction of the coils can be more readily visualized from theperspective view of FIGURE 3.

The connections for supplying power to the apparatus thus described areillustrated in FIGURE 4. These comprise means for developing a brief butintense pulse of current through the two coils and for furtherdeveloping a voltage pulse, which will break down the spark-gap, whilethe current is flowing. There are several well known methods ofdeveloping such pulses, that shown being one conventional type which issuitable for the purpose. Power for developing the current pulse may bederived from an ordinary 60-cycle power line which feeds a rectifierpower-supply 67, of substantially conventional type, to develop directcurrent at a potential of from 1 to 25 kilovolts, depending upon theduty to be imposed upon the system as a whole. The power-supply 67connects to a pulse-forming network, generally designated by thereference character 69, through a current-limiting resistor 71. Thenetwork comprises series inductive elements 73 bridge by capacitors 75,in accordance with ordinary delay line practice, differing from theusual types of delay line only in that the capacitors are larger and theinductors smaller than would usually be used to give the required delayor pulse length of, say, 10 microseconds, in order to match the lowimpedance of the coils.

The line 69 connects to the coils 55 and 61 in series, through aspark-gap switch 77. This spark-gap can be fired by means of a startingtrigger 79 which, by firing an auxiliary gap by adding a potential tothat which is developed across the charged line, starts ionization inthe main gap and thus initiates the main discharge. The use of suchtriggers is familiar in radar practice and in other utilizations ofpulse techniques; the constructions of both the spark-switch and thetriggering mechanism are conventional and therefore need not bedescribed in detail. The trigger itself may be actuated at any desiredrepetition rate by a self-contained oscillator, an external oscillator,or it may be operated on the one shot principle by closing a manualswitch.

The current in the coils 55, 61 depends upon the voltage to which thedelay line 69 is charged and upon the effective impedance of the coilsand their attached leads. Although the capacity between the leads ishigh, the impedance of the circuit through which the line discharges islargely inductive. Numerically, however, the inductance of the two coilsis very small, even in terms of microhenries. Once the gap 77 is brokendown its effective resistance is negligible and with substantially thefull value of the voltage delivered by the power supply 67 effectiveacross the inductance of the coils, discharge current pulses of manythousands of amperes can be maintained through the coils during theinterval required to discharge the line. With short current pulses ofthe contemplated duration, the current is concentrated near the internalsurfaces of the coils by skin effect and the magnetic field developed bya current of this magnitude is all forced through the very smallinternal diameter of the coils; using coils of this type fluxes havebeen developed and measured as high as 10 million (10 gauss at thislocation.

In order to cause the ionizing spark to jump the gap between electrodes25 and 29 while this magnetic field persists, the discharge of the delayline 69 may be used to trigger the spark discharge. The latter isderived, preferably from the same power line as that feeding therectifier power supply 67, through a similar high-voltage rectifierpower supply 81, which, however, preferably operates at a higher voltagethan the supply 67, i.e., at from 20 to 100 kilovolts. Supply 81 iscoupled through a current-limiting resistor 82 to a delay-line 83 of thesame general type as the line 69, including series inductors 85 andshunt capacitors 87. This line is designed to give a very slightlyshorter discharge time than the line 69, say 9 microseconds if line 69develops a l0-microsecond pulse. Line 83 connects to the spark gapwithin the container through a spark-switch 89, of the same type as theswitch 77. This switch, however, is triggered by means of a pulsesupplied through a coil 91 which is coupled to one of the coils 73,preferably that at the end of delay line 69 nearest its point ofdischarge. The initiation of the current pulse through the line 69 thustrips a trigger 93, generally similar to the trigger 79, and initiates apulse which breaks down the gap 89 and initiates the discharge. Thespark can, however, be triggered at a later epoch by coupling the coil91 with one of the coils 73 which is located farther from the dischargeend of the line, as indicated, for example, by the position of the coil91.

The pulsing may be triggered by any type of timing means which willstart the spark after the magnetic field has reached a predeterminedvalue, or, as hereinafter explained, it may be preferred in certainapplications to ionize the gas in advance of the magnetic field pulse inwhich event the sparking pulse may be employed to trigger the currentpulse through the coils. Suitable timin means may includemultivibrators, oscillators with phase selecting circuits, as well asdelay lines actuated by appropriately shaped pulses and other equivalentknown circuitry.

The arrangement shown is designed to give substantially rectangularpulses of both voltage and current. This is desirable but not anecessary feature. The magnetic fields can build up gradually, as longas their build up is rapid enough to confine the ions at any giveninstant. For many purposes simple condenser discharges can besubstituted for formed pulses, in either the magnetic-field generatingcircuit or the spark circuit. It is not even necessary that a DC sparkbe used; in most applications of the invention the primary function ofthe spark is to supply thermal energy to the magnetically-confined gas,and this can be accomplished by an oscillatory discharge as well as bydirect current. The use of an oscillatory spark may even be of advantagein certain applications of the invention.

It will be realized that the circuit of FIGURE 4 15 only one of severalwhich may be used and which are, in general, well known. High-powerpulsing circuits have become commonplace in connection with radarequipment and for this reason it is considered to be unnecessary todescribe the trigger generators or the parameters used in the pulseforming networks in detail; reference may be made to standard works onradar pulsing circuits for detail omitted in the present description.

The apparatus of FIGURES 1 and 2 has been shown with the coils 61 and 55connected in series-opposing relationship as indicated in the enlargedfragmentary view of FIGURE 5, with the current direction in the twocoils opposite, so that the lines of force in the reaction space definedby the diameter of the opening 57 and the space between the two coilshave a polar axis of cylindrical symmetry and follow the paths asindicated generally by the light curved lines 95 within the gap. Withthis arrangement, it will be seen that there is a radial bulge in theflux lines near the median transverse plane of the field, thus defininga small, nearly field-free region, in the reaction space, on the axis ofthe coils and midway between them. The flux lines are substantially moreconcentrated near the axial ends of the reaction space than in themedian transverse plane. The general direction of the electric fielddeveloped across the spark gap at the instant of the voltage pulse isindicated by the dotted lines 97 spanning the spark-gap. When the fullvoltage is developed across the gap, ions carrying the discharge canpass between the points, along the axis, without being deflected even bythe very powerful field in the gap, while those which are not directedprecisely along the axial direction will travel through spiral paths butwith minimum deflection. Once the discharge is started, the gas in thesubstantially field-free reaction space at the center of the gap isquickly ionized and heated, the particles receiving energy which drivesthem at velocities depending upon their acquired energy and indirections which rapidly tend to become random. Because they are ionizedand thus carry charges, they will, in general, upon entering the fieldsurrounding the reaction space, be deflected and returned into thereaction space. This holds for all particles except those proceedingdirectly along the axis of the spark gap or those traveling in atransverse plane exactly at the center of the gap, where they can travelparallel to the radial magnetic field midway between the two coils. Theproportion of the ions traveling in either of these directions isrelatively small and very little energy escapes from the gap in thismanner, particularly since repeated collisions constantly change thedirections of the ions so that it is only those near the edge of theheated space which have reasonable probability of escape in thetransverse direction. With fields of the magnitude which can readily beobtained with the mechanism here described, ions of the lighter gaseshaving thermal energies as high as 10,000 electron volts will, ingeneral, be returned to the reaction space, still retaining theirthermal energy.

The effect of the deflection of the ions is to enlarge the field-freespace, the magnetic fields developed by the moving particles adding tothe field strength in the region between the particle and the coil whichgenerates the field and subtracting from the field on the side of theion path more distant from the coil. Therefore, although the reactionspace may not have actually been field-free at the initiation of thedischarge, it approaches this condition more nearly as time goes on andthe number and velocity of the ions increases. Effectively the lines offorce of the field through the coils are crowded closer to the coilsthemselves.

Since the ions cannot penetrate the magnetic field and strike the coilsthey do not lose energy to them. The points of the spark-gap are heated,as is the case with any spark, but the total number of ions which dostrike the points is little greater than that which would be developedby a spark of the same voltage under ordinary conditions.

It is not essential to the invention that the coils 55 and 61 be soconnected as to set up their magnetic fields in opposite directions.They can be connected in seriesaiding relationship so that the fieldsboost instead of buck, in which case the general configuration of thefield in the vicinity of the spark, while also cylindrically symmetricalwith respect to the common axis of the coils, will be that shown inFIGURE 6. Under such circumstances, the flux lines also have a radialbulge near the median transverse plane of the field and aresubstantially more concentrated near the axial ends of the reactionspace than in the median transverse plane, but there is initially nofield-free region on the reaction space, the ions have certaindefinitely preferred directions of motion, and immediate thermalizationor randomness of direction does not occur. Some of the initial ions ofthe discharge, however, inevitably enter the magnetic field withcomponents of motion transverse to the lines of force, and are therebyforced into spiral paths which crowd the field of the coils toward thecoils and thus tend to form their own field-free space.

It will be apparent that the arrangement of FIGURE 6 has the advantagethat there is no escape path for the ions through the median planebetween the two coils, but because of the very small proportion of theions whose velocities are oriented in this plane and which are also in aposition where they can escape before collision with other ions deflectsthem, the advantage is not of major importance. On the other hand, theconfiguration of FIGURE gives the coil system a lower inductance thanthat of FIGURE 6, the mutual inductance between the coils beingsubtractive instead of additive, and therefore less power is required toestablish a current pulse of the same value in the inductance coilstructure of FIGURE 5 than in that of FIGURE 6. The power expended inthe coil circuit does not go into heating the gas and thereforerepresents a loss.

FIGURE 7 illustrates how a field of similar configuration to thatillustrated in FIGURE 6 may be generated by means of a single coil, inplace of the dual coils shown in FIGURES 5 and 6. In this case the coilmay be formed with a steel core 100, having within it a channel 102,wherein a coolant or energy-transfer fluid may be circulated. The coreis preferably covered with a highly conductive layer 104, preferably ofcopper. The internal edges of the coil, surrounding the reaction space,are provided with a groove, leaving the central opening wherein thefield is established smaller at its two edges than in the median line ofthe coil. Owing to the repulsion between the lines of force, this leavesa central space between the coil edges where the field is Weaker than atthe ends of the central aperture into which electrodes 25 and 29project.

The mechanism by which the field contains the ionized gas, in eachembodiment of the invention, is that a charged particle traversing thefield is the equivalent of an electric current. A force is thereforeexerted upon it, at right angles to both its direction of motion and thedirection of the field, which deflects it in an approximatelysemi-circular orbit and returns it to the relatively field-free reactionspace. The pressure of a gaseous medium is, of course, the force perunit area which it exerts against the surface containing it. It isproportional to the square of the average velocity of the particlesstriking the walls of the area, which, in turn, is proportional to theirabsolute temperature. The pressure is further proportional to the numberof such particles and to their mass. Where the walls which contain thegas are the lines of force of a magnetic field the particles mustpenetrate the field deeply enough to have their velocity reversed.

In their motion the charged particles set up magnetic fields of theirown in such sense as to decrease the field strength within their orbitsand increase the field strength externally thereof, in effect crowdingthe lines of force of the initial field closer to the conductorscarrying the exciting current. The number of lines of force lyingbetween the original reaction space and the walls of the conductor isnot changed by this process, with the result that the flux density isprogressively increased and the constraining effect of the encompassingfield increases accordingly.

Disregarding this crowding effect for the moment, and considering thatthe field surrounding the reaction space is homogeneous and constant,since force is the rate of change of energy with distance, the force perunit area which the field will withstand is numerically equal to theenergy density. Therefore, where P is the pressure in dynes per squarecentimeter and B is the magnetic field strength in gauss:

In order that the particles be subjected to this force, they mustpenetrate the field to a depth which depends on the field strength, andif they are to be returned to the reaction space so that they canactually be said to be contained, this depth must be fairly small incomparison to the dimensions of the reaction space itself. Stillconsidering the case of a uniform, homogeneous field, the depths ofpenetration (i.e., the radii of curvature of the particle orbits) can becomputed from the velocities corresponding to their temperatures and thefield strength. For deuterium nuclei, these radii, at velocitiescorresponding to various temperatures and various field strengths, aretabulated be low, the field B being in gauss, the temperatures T indegrees Kelvin and the radii r in millimeters:

It will be seen from above that a field of even 10 gauss is sulficientto impart to the deuteron nuclei a radius of curvature sharp enough toreturn most of them into a reaction space corresponding to a onemillimeter sphere even at a temperature of fifty million degrees Kelvin.With a field of 10 gauss the radii of curvature are only millimeter andsubstantially all of the nuclei will be returned to a reaction space ofthis size.

Owing to the large number of charged particles contained in the reactionspace and the crowding of the lines of force mentioned above, the fieldsWill not be homogene ous. Within the reaction space there will be a zoneof decreasing field strength, merging gradually into a zone of increasedfield strength. To a first approximation, if the initial field strengthis high enough so that the number of lines of force between it and theconductors is sufiicient to reverse the normal component of velocity andreturn the ions to the space at the maximum temperature to be contained,then as long as they do not exceed that temperature they can never reachthe conductors.

From the above it will be seen that a field encloses or encompasses areaction space if it will return ions to that space from which the fielditself has been displaced. T0 at least a first approximation the ionizedgas obeys the ordinary gas laws:

where P is the pressure, V is the volume, T the absolute temperature indegrees Kelvin, and R is a constant which depends upon the gas. Thatthis is only afirst approximation is due to fact that the composition ofthe gas changes as the action proceeds. Qualitatively, however, the gastends to expand and crowd the lines of force as its temperatureincreases; in other words, the volume of the heated gas will increaseslightly with the increase in size of the field-free space caused by iondeflection. This increase in volume may, however, be made up by theentry of additional molecules of un-ionized gas from the surroundingbody, since such un-ionized particles can penetrate the magnetic fieldfrom any direction without deflection. Once they have entered andacquired energy by collision with the thermally agitated particleswithin the space, they too become ionized and cannot again escape. Themagnetic field therefore acts as a semi-permeable membrane, and thepressure within the volume of heated gas can build up by a processcomparable to osmosis.

The degree to which the reaction space can expand depends on the form ofthe apparatus used. With the apparatus of FIGURES 1 and 2 the field canbe forced back into the interspace between the two coils, regardless ofwhether the coils are connected in bucking or boosting relationship.With the coil arrangement shown in FIG- URE 7, however, the field cannotbe forced back into the conductor and the expansion is therefore limitedby the size of the groove within the coil periphery. Expansion of thereaction space results in a reduction of temperature, in accordance withthe gas law as given above, and therefore somewhat higher temperaturesmay be attained with a single coil than with dual coils connected ineither relationship shown.

It will thus be seen that during the period when the current pulsethrough the coils persists, the ionized particles cannot escape from therestraining field to carry away energy by convection or to strike thesurrounding structure (with the exception of the spark pointsthemselves) to cause any material loss of energy by conduction.

1. APPARATUS FOR PRODUCING HIGH TEMPERATURE COMPRISING: AN INDUCTANCECOIL STRUCTURE ENCOMPASSING A MAGNETIC-FIELD-FREE REACTION SPACE; MEANSFOR PRODUCING AN ELECTRIC CURRENT PULSE IN SAID INDUCTANCE COIL STRUCTUEOF DEVELOP A CONCENTRATED MAGNETIC FIELD, OF AN INTENSITY OF AT LEAST OFTHE ORDER OF 106 GAUSS, SUBSTANTIALLY ENCOMPASSING SAID REACTION SPACE;AND MEANS FOR PRODUCING A CLOUD OR PLASMA OF IONS IN SAID REACTION SPACEDURING THE EXISTENCE OF SAID MAGNETIC FIELD.